Surprisingly, most E46 owners are still in them, only a few have transitioned.

So, you are privy to confidential BMW, auto industry or EPA information that proves this?
Since about 1/3 of BMW E46 3-series were leased (I can give you a reference for that if you want it), it kind of calls your blanket statement "few" into question.

Frankly, I simply don't believe that you can prove your assertions. Even anecdotally, look at the number of "newbie, just bought a ..." that are posted in this forum.